You're in danger of falling into the trap of believing the customer is dumb, because they are choosing to use a supplier who - in your opinion - is no good. No business ever became successful with that sort of thinking. Instead, start thinking the customer is always right and will buy what they prefer, for lots of reasons, not just image quality. At the end of the day, if some other Tog is getting business while you're not, then they ARE doing a better job than you.
Start to think in marketing terms, which should always begin by trying to see the world through the eyes of the customer. Once you think you have a handle on what the market needs, you set about trying to invent a product or service to meet that need. Also, remember that markets are not homogenous, with every customer wanting exactly the same thing. Markets are actually groups of mini-markets if you look at them closely. Looked at like this, you will see that the 'wedding photography market' can be 'segmented' (divided up) into discrete markets where the customer wants something slightly different - some want conventional images, others might want 'quirky', some want fancy albums, others just want a CD with a bunch of images on, some want a 'name' and a top-level service, others want a budget package.
Once you understand the market you want to aim at, you need to create a 'competitive advantage' - you make yourself different in some way. This doesn't have to be about shooting style. It could be more about the way you do business or how you treat clients. Creativity isn't just about the images!
Finally, you decide how to promote your business - how you get your message to the market. A website is a given these days, but remember that a website is a 'passive' device. It doesn't go looking for clients; they have to go looking for your website. Hence, there really is no substitute to getting out there and talking to people, at wedding exhibitions, social events, wherever. This WILL be a hard slog. Don't expect to transform your future overnight. It might take two years to really get your name widely known. Basically though, there is no substitute for effort.
So to summarise: the customer is always right, even when they're wrong. You need to accept that and provide them with what they want.